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Rewrite Saturating in terms of CheckedAdd/CheckedSub #8515

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Rewrite Saturating in terms of CheckedAdd/CheckedSub #8515

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63 changes: 25 additions & 38 deletions src/libstd/num/num.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -468,55 +468,42 @@ impl<T: Zero> Zero for ~T {
}

/// Saturating math operations
pub trait Saturating: Int {
pub trait Saturating {
/// Saturating addition operator.
/// Returns a+b, saturating at the numeric bounds instead of overflowing.
fn saturating_add(self, v: Self) -> Self;

/// Saturating subtraction operator.
/// Returns a-b, saturating at the numeric bounds instead of overflowing.
fn saturating_sub(self, v: Self) -> Self;
}

impl<T: CheckedAdd+CheckedSub+Zero+Ord+Bounded> Saturating for T {
#[inline]
fn saturating_add(self, v: Self) -> Self {
let x = self + v;
if v >= Zero::zero() {
if x < self {
// overflow
Bounded::max_value::<Self>()
} else { x }
} else {
if x > self {
// underflow
Bounded::min_value::<Self>()
} else { x }
fn saturating_add(self, v: T) -> T {
match self.checked_add(&v) {
Some(x) => x,
None => if v >= Zero::zero() {
Bounded::max_value::<T>()
} else {
Bounded::min_value::<T>()
}
}
}

/// Saturating subtraction operator.
/// Returns a-b, saturating at the numeric bounds instead of overflowing.
#[inline]
fn saturating_sub(self, v: Self) -> Self {
let x = self - v;
if v >= Zero::zero() {
if x > self {
// underflow
Bounded::min_value::<Self>()
} else { x }
} else {
if x < self {
// overflow
Bounded::max_value::<Self>()
} else { x }
fn saturating_sub(self, v: T) -> T {
match self.checked_sub(&v) {
Some(x) => x,
None => if v >= Zero::zero() {
Bounded::min_value::<T>()
} else {
Bounded::max_value::<T>()
}
}
}
}

impl Saturating for int {}
impl Saturating for i8 {}
impl Saturating for i16 {}
impl Saturating for i32 {}
impl Saturating for i64 {}
impl Saturating for uint {}
impl Saturating for u8 {}
impl Saturating for u16 {}
impl Saturating for u32 {}
impl Saturating for u64 {}

pub trait CheckedAdd: Add<Self, Self> {
fn checked_add(&self, v: &Self) -> Option<Self>;
}
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